Static shielding film

ABSTRACT

Flexible sheet materials and envelopes are described which are useful for packaging electronic components. The sheet material includes an electrically insulating film with a conductive layer on the upper surface and an antistatic layer carried by the lower surface The antistatic layer includes a fluoroaliphaticsulfonamide polyether compound. Optionally a tie layer may be included between the film and the antistatic layer.

This is a continuation of co-pending application Ser. No. 07/724,738filed on Jul. 2, 1991, now abandoned, which is a continuation of priorapplication Ser. NO. 07/264,333, filed Oct. 28, 1988 now U.S. Pat. No.5,043,195.

FIELD OF THE INVENTION

This invention relates to static shielding film constructions. Moreparticularly, this invention relates to film constructions useful formaking packages of the type used for protective packaging of electroniccomponents such as metal oxide semiconductors.

BACKGROUND OF THE INVENTION

The protection of electronic components (such as metal oxidesemiconductors) from electrostatic discharges during storage andtransport prior to installation has been recognized as extremelyimportant. One means of protecting such components involves the use of aprotective envelope such as is described in U.S. Pat. Nos. 4,154,344 and4,156,751. Such type of envelope includes a transparent sheet materialhaving an antistatic layer on one surface and a conductive layer on theopposite surface.

The sheet material can be polyester film and a heat sealable layercomprising polyethylene. However, the effectiveness of the sheetmaterial as static shielding film can be affected by the manner in whichthe antistatic layer is secured to the polyester film.

There has not heretofore been provided flexible sheet material or apackaging envelope having the advantages provided by the presentinvention.

SUMMARY OF THE INVENTION

In accordance with the present invention there is provided, in oneembodiment, a flexible sheet material which is adapted for packagingelectronic components and which is sufficiently transparent to enablevisual identification of components through the sheet material. Thesheet material comprises:

(a) self-supporting electrically insulating film having a volumeresistivity of at least about 10¹⁰ ohm-centimeters; said film havingupper and lower major surface;

(b) an electrically conductive layer carried by said upper surface ofsaid film; said conductive layer providing a surface resistivity nogreater than 10⁴ ohms per square;

(c) optionally, a tie layer carried by said lower surface of said film;and

(d) an antistatic layer secured to said tie layer, if a tie layer ispresent, or to the lower major surface of the film if no tie layer ispresent, said antistatic layer comprising a polymer having dispersedtherein a fluoroaliphaticsulfonamide polyether compound, wherein saidantistatic layer provides a surface resistivity in the range of 10⁷ to10¹⁴ ohms per square.

The sheet material can be easily formed into a strong hermeticallysealable envelope which is useful for protecting electronic components(e.g., metal oxide semiconductors). Such an envelope is capable ofshielding an electronic component from external electrostatic fields,provides a path to ground for external static electrical chargescontacting the envelope, provides a high impedance to preventelectrostatic charges outside the envelope from reaching the electroniccomponent within the envelope, provides for draining of anyelectrostatic charges at the inner surface of the envelope that may havedeveloped during manufacturing and packaging, restricts development ofelectrostatic charges due to relative movement between the electroniccomponent and the inner surface of the envelope and provides a highimpedance path for the controlled discharge of such electrostaticcharges if they do occur, and enables visual identification of theelectronic component in the envelope. Also, the envelope does not shedparticles which may be considered contaminants.

As used in this invention, the term "envelope" refers to any completeenclosure formed by one or more sheets of the sheet material which havetheir edges secured together. The enclosures can be any shape requiredto enclose an electronic component. Preferably the envelope is formedfrom only one sheet of the sheet material in order to ensure electricalcontinuity of the electrically conductive layer over the entire outersurface of the envelope and continuity of the antistatic layer over theentire inner surface of the envelope.

In the sheet material of this invention the insulating film (e.g.,polyester) is optionally adhered to the antistatic layer by means of atie layer (preferably an acrylate polymer). The antistatic layerincludes a fluoroaliphaticsulfonamide polyether compound Conventionalantistatic compounds are not effective in the antistatic layer whenthere is a tie layer present as described herein.

The antistatic layer in the sheet material of this invention hasimproved electrical properties such that it remains conductive at lowhumidities (i.e., less than 10%). Also the antistatic compounds usedherein are non-corrosive and noncontaminating. A tie layer may beincluded between the antistatic layer and the insulating film withoutdeleterious effect on the desired surface resistivity of the antistaticlayer.

Other advantages of the sheet material and envelope of the inventionwill be apparent from the following description and the appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail hereinafter with reference tothe accompanying drawings wherein like reference numbers refer to thesame parts throughout the several views and in which:

FIG. 1 is a perspective view of an envelope of the present invention;

FIG. 2 illustrates the use of the envelope of FIG. 1 for packaging anelectronic component;

FIG. 3 is an enlarged fragmentary sectional view of a preferredembodiment of sheet material of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1 and 2 there is illustrated a preferred type of envelope 10 ofthe invention comprising a sheet material 11 of the invention which hasbeen folded upon itself along fold line 12. Side edges 13, 14 and 15 ofopposed walls 16 are brought into alignment, as illustrated. The edgeportions 17 of the walls are fused together (e.g., by heat sealing) toform an envelope having an opening at one end between the pair ofaligned edges 15.

An electronic component 18 may be easily inserted into the envelopethrough the opening, and then the aligned edges 15 can be fused togetherto form edge 19 to seal the component in the envelope, as illustrated,in FIG. 2.

FIG. 3 illustrates the preferred form of sheet material 30 of theinvention. This sheet material comprises a self-supporting electricallyinsulating film 32. On the upper surface of the film there is providedan electrically conductive layer 33. Over the conductive layer therepreferably is an abrasion-resistant coating 34 which presents an exposedsurface 34A.

The film 32 has a volume resistivity of at least 10¹⁰ ohm-centimeters(and preferably at least 10¹⁵ ohm-centimeters). The film 32 ispreferably biaxially oriented polyester having a thickness in the rangeof about 10 to 50 microns.

The abrasion-resistant coating 34 is sufficiently tough to restrictabrasion of the conductive layer without impairing surface conductivityof the sheet material. A suitable thin abrasion-resistant coating isdescribed in U.S. Pat. No. 3,118,781, incorporated herein by reference.The coating may be about 0.1 to 1 micron thick, for example.

The conductive layer 33 comprises metal or metal containing compoundsand provides a surface resistivity no greater than 10 ⁴ ohms per squarewhile still affording with the other layers of the sheet material alight transmittance sufficient to enable visual identification of anelectronic component through the sheet material (i.e., a lighttransmissivity of at least 25%, and preferably no less than 40%). Vapordeposition in vacuum by electron beam is the preferred method ofapplying the conductive layer to the film 32. Sputtering or electrolessplating may also be used.

Various metals may be used for conductive layer. Thin metal layers areuseful because they can provide low resistivity and adequate lighttransmission. Nickel is particularly preferred because it can providelow resistivity of about 90 to 550 ohms per square in thicknesses whileproviding about 50 to 60% light transmission. Aluminum and copper couldalso be used, although they are not preferred. Inconel and chromiumcould also be used but have higher surface resistivity. Silver and goldcould also be used but are more expensive.

Metallic compounds could also be used such as tin and indium oxides,cuprous chloride, and cuprous iodide.

Secured to the lower surface of film 32 is a tie layer 35 which adheresantistatic layer 36 to film 32. The tie layer 35 preferably comprises anacrylate polymer at a thickness in the range of about 5 to 15 microns(preferably about 7 to 10 microns). The presence of a tie layer isoptional.

The tie layer and the antistatic layer are preferably co-extruded, afterwhich the tie layer is adhered to the polyester film by passing thepolyester film and the tie layer/antistatic layer composite through niprollers. The tie layer/antistatic layer composite can be passed underultraviolet lamps while being passed over a heated drum to improve itsbond to the polyester film. Alternatively, the tie layer and theantistatic layer can be extruded separately and then pressed together toform a composite which is then adhered to the polyester film.

The tie layer preferably comprises an acrylate polymer such asethylene-acrylic acid copolymers or ethylene/methacrylic acid copolymersor other acrylate polymers which are tacky and which have a volumeresistivity of at least 10¹⁰ ohm-centimeters.

The antistatic layer preferably comprises low density polyethylene(e.g., 1550P from Eastman Kodak) and 0.05 to 10% by weight (morepreferably 0.15 to 1%) of a fluoroaliphaticsulfonamide polyethercompound. A linear low density polyethylene works very well in theantistatic layer because it has very good heat-sealing properties.Optionally there may also be included up to about 2% by weight of asurfactant comprising a non-ionic polyether compound (e.g., polyethyleneoxide or polypropylene oxide derivatives). The surfactant is helpfulbecause it assists in reducing the tribocharging characteristics of theantistatic layer. Tribocharging can result in build-up of static chargesin the antistatic layer due to frictional forces (e.g., as occurringwhen an object is rubbed against the antistatic layer). Two common typesof useful surfactants are Tergitol NP-10 or Igepal 530 (a nonylphenolethyoxylate) and Carbowax 400 (a polyethylene, glycol).

It has also been noted that the use of the fluoroaliphaticsulfonamidepolyether compounds described herein in the antistatic layer reduces thecoefficient of friction of such layer. This is helpful when working withenvelopes made of the sheet material.

It is also possible to emboss the sheet material of the invention. Thismakes it easier to handle when it is used in envelopes for packagingelectronic components.

The fluoroaliphaticsulfonamide polyether compounds which are useful inthe antistatic layer of the sheet material of this invention are of theformula ##STR1## where y and n are each in the range of 0 to 100 (morepreferably 4 to 20); wherein y+n is at least 2; wherein R is hydrogen,alkyl, aryl, aralkyl, aminoalkyl, or hydroxyalkyl; wherein R'' and R'''are selected from ethylene and propylene; and wherein R' is hydrogen,alkyl, aryl, aralkyl, alkaryl, aminoalkyl, hydroxyalkyl, alkoxy, orperfluorosulfonamido. Where y and n units are both present in thecompound they may be either randomly distributed throughout and/or theymay be present in blocks of y and n units.

The fluoroaliphatic radical, R_(f), is a fluorinated, stable, inert,non-polar, preferably saturated, monovalent moiety which, ifsufficiently large (e.g., 5 or more carbon atoms), is both hydrophobicand oleophobic. It can be straight chain, branched chain, or, ifsufficiently large, cyclic, or combinations thereof, such asalkylcycloaliphatic radicals. The skeletal chain in the fluoroaliphaticradical can include catenary divalent oxygen atoms and/or trivalentnitrogen atoms bonded only to carbon atoms. Generally R_(f) will have 1to 30 carbon atoms, preferably 4 to about 12 carbon atoms, and willcontain about 40 to 78 weight percent, preferably 50 to 78 weightpercent, carbon-bound fluorine. The terminal portion of the R_(f) grouphas preferably at least one trifluoromethyl group, and preferably has aterminal group of at least three fully fluorinated carbon atoms, e.g.,CF₃ CF₂ CF₂ -. The preferred R_(f) groups are fully or substantiallyfluorinated, as in the case where R_(f) is perfluoroalkyl, C_(m)F_(2m+1) -.

More preferably the polyether compound is of the formula ##STR2## wherem is an integer of 1 to 12; n is in the range of 2 to 20; R is hydrogen,alkyl, aryl, aralkyl, aminoalkyl, or hydroxyalkyl; and R' is hydrogenalkyl, aryl, aralkyl, alkaryl, aminoalkyl, hydroxyalkyl, alkoxy, orperfluorosulfonamido.

Specific polyether compounds of the above formulas include those listedbelow.

    __________________________________________________________________________    Compound                                                                      Number                                                                        __________________________________________________________________________    (1)                                                                                  ##STR3##                                                               (2)                                                                                  ##STR4##                                                               (3)                                                                                  ##STR5##                                                               (4)                                                                                  ##STR6##                                                               (5)                                                                                  ##STR7##                                                               (6)                                                                                  ##STR8##                                                               (7)                                                                                  ##STR9##                                                               (8)                                                                                  ##STR10##                                                              (9)                                                                                  ##STR11##                                                              (10)                                                                                 ##STR12##                                                              (11)                                                                                 ##STR13##                                                              (12)                                                                                 ##STR14##                                                              (13)                                                                                 ##STR15##                                                              (14)                                                                                 ##STR16##                                                              __________________________________________________________________________

Compounds of the foregoing types may be easily prepared by reacting aperfluorosulfonyl fluoride compound with a polyether amine. Othermethods of preparation may also be used, if desired. For example,procedures for preparing perfluorosulfonamide compounds which arederivatives of amines are described in U.S. Pat. 2,915,554, incorporatedherein by reference. Some sulfonate salt may also be produced in thereaction, but such salt is not detrimental to the ability of the desiredfluoroaliphaticsulfonamide polyether compound to function as anantistatic compound in this invention.

There may also optionally be included in the antistatic layer a smallamount of lithium perfluorosulfonate salt which is useful in increasingantistatic or conductive properties of a plastic film to which theantistatic layer is applied, especially at low humidity (e.g., less thanabout 15% relative humidity). When using a water soluble or long chainperfluorosulfonamide polyether compound in the antistatic layer of afilm construction of the invention, the presence of a lithiumperfluorosulfonate salt can improve seam strength of packages made fromsuch film.

The lithium perfluorosulfonate salt which is useful herein is of theformula

    R.sub.f SO.sub.3 Li

wherein R_(f) is a fluoroaliphatic radical as described above havingfrom 1 to about 30 carbon atoms. Lithium disulfonate salts may also beused, e.g., LiO₃ S--C_(n) F_(2n) --SO₃ Li, where n is 1 to about 30.

The amount of lithium salt which may be included in the antistatic layermay vary (e.g., from about 0.01 to 1% by weight based on the weight ofthe antistatic layer).

Compounds of the type illustrated by compounds (1) and (4) above are thesubject of copending application Ser. No. 07/263,719, now abandoned,filed of even date, and incorporated herein by reference.

Compounds of the type illustrated by compounds (6), (7), and (12) aboveare the subject of copending application Ser. No. 07/263220, nowabandoned, filed of even date, and incorporated herein by reference.

The invention is further illustrated by means of the following exampleswherein the term parts refers to parts by weight unless otherwiseindicated.

EXAMPLES 1-23

Various sheet materials are prepared comprising a polyester film, apolyethylene layer, and an antistatic compound contained in thepolyethylene layer. The polyethylene used was either low density (LD) orlinear low density (LL). A tie layer, if used, was an acrylate polymeridentified in the following Table I as CXA-3101 (an ethylene basedacrylate polymer commercially available from Dupont); EAA-459, EAA-435,EAA-3440 (ethylene/acrylic acid copolymers commercially available fromDOW); or EMA-2207 (ethylene/methacrylic acid copolymer commerciallyavailable from DOW).

The resistivity (ohm/square) of the antistatic layer at 10% relativehumidity and 50% relative humidity are shown in the table. The type ofantistatic compound is also shown in the table.

                  TABLE I                                                         ______________________________________                                        Ex-                                                                           am-                            Resistivity (ohm/square)                       ple  Antistat   %      Tie Layer                                                                             50% R.H.                                                                              10% R.H.                               ______________________________________                                         1   Varstat    0.14   None    3.8 × 10.sup.11                                                                 6 × 10.sup.12                         K22                                                                       2   Varstat    "      CXA-3101                                                                              >10.sup.15                                                                            >10.sup.15                                  K22                                                                       3   Varstat    "      EAA 459  "       "                                          K22                                                                       4   Varstat    "      EAA 435  "       "                                          K22                                                                       5   Kemamine   "      None    3.7 × 10.sup.11                                                                 6 × 10.sup.12                         650                                                                       6   Kemamine   "      CXA-3101                                                                              8.9 × 10.sup.13                                                                 >10.sup.15                                  650                                                                       7   Kemamine   "      EAA-459 >10.sup.15                                                                             "                                          650                                                                       8   Kemamine   "      EAA-435  "       "                                          650                                                                       9   Varstat    "      None    8.9 × 10.sup.10                                                                 7.4 × 10.sup.12                       K22                                                                      10   Varstat    "      EMA-2207                                                                              7.4 × 10.sup.12                                                                 >10.sup.15                                  K22                                                                      11   Compound 9 "       "      4.3 × 10.sup.11                                                                 3.6 × 10.sup.12                  12    "         "      CXA-3101                                                                              1.3 × 10.sup.12                                                                 9.9 × 10.sup.12                  13    "         "      EAA-3440                                                                              1.5 × 12.sup.12                                                                 7.8 × 10.sup.12                  14   Varstat K22                                                                              "      EMA-2207                                                                              2 × 10.sup.14                                                                   >10.sup.15                             15   Compound 9 "       "      1.7 × 10.sup.12                                                                 6.5 × 10.sup.12                  16   Compound 11                                                                              0.15   None    1.1 × 10.sup.12                                                                 3.4 × 10.sup.12                  17    "         "      EMA-2207                                                                              8.3 × 10.sup.11                                                                 7.8 × 10.sup.12                  18    "         "      None    1.5 × 10.sup.12                                                                 4.3 × 10.sup.12                  19    "         "      EMA-2207                                                                              2.7 × 10.sup.12                                                                 1.4 × 10.sup.13                  20   Compound 2 "       "      4.6 × 10.sup.11                                                                 1.5 × 10.sup.12                  21   Compound 3 "       "      4.0 × 10.sup.11                                                                 1.1 × 10.sup.12                  22   Compound 8 "       "      1.1 × 10.sup.12                                                                 6.6 ×  10.sup.12                 23   Compound 5 "       "      2.4 × 10.sup.11                                                                 1.5 × 10.sup.12                  ______________________________________                                    

In the foregoing examples, Varstat K22 is a commercially-availableantistatic compound from Sherex and is identified asN,N-Bis(2-hydroxyethyl)alkyl amine (an ethoxylated cocoamine). Kemamine650 is also a commercially-available antistatic compound available fromHumko Chemical and is chemically similar to Varstat K22.

In Examples 14, 15, 18 and 19 the polyethylene layer comprised linearlow density polyethylene. In the other examples low density polyethylenewas used.

The foregoing data illustrates that when a tie layer is used to securethe polyethylene to the polyester film the commercially-availableantistatic agents are not effective at low humidity. On the other hand,the perfluorosulfonamide polyether compounds are very effective asantistatic agents even at low humidity.

EXAMPLE 24

Many static shielding films were prepared with and without a tie layerpresent between the antistatic layer and the electrically insulatingfilm. Various amounts of compound 11 were used as the antistaticcompound in the antistatic layer of several of the films, and 0.14% byweight of Varstat K-22 was used as a conventional antistatic compound intwo other films.

The insulating film used in all of the constructions was polyesterhaving a thickness of about 50 microns. The tie layer used was EMA-2207at a thickness of about 8 microns. The antistatic layer in eachconstruction was low density polyethylene having a thickness of about 43microns. The antistatic compound used in each construction was mixedwith the polyethylene resin prior to extrusion of the antistatic layer.

After the various film constructions were prepared they were tested forsurface resistivity of the antistatic layer at 10% relative humidity andalso at 50% relative humidity. Samples were also tested for T-peeladhesion (between the antistatic layer and the insulating film) as wellas % delamination. Some samples were aged for 10 days at 150° F. beforetesting; other samples were allowed to remain at room temperature for anequal length of time before testing (referred to as "Initial" in thetable). The results are shown in Table II where FC denotes compound 11whose structure is shown above.

                                      TABLE II                                    __________________________________________________________________________                                             Varstate K-22                                   FC (% by weight)              With  Without                                   With Tie Layer Without Tie Layer                                                                            Tie Layer                                                                           Tie Layer                      __________________________________________________________________________    T-Peel     0.2  0.4  0.6  0.2  0.4  0.6                                       (lbs/in. at break)                                                            Initial    12.6 13.5 12.0 17.4 17.0 17.0 12.9  14.5                           Aged       10.6 11.6 10.8 17.6 16.7 16.5 13.5  8.0*                           % Delam.                                                                      Initial    3    2    4    1    2    2    25*    40*                           Aged       2    1    20   0    0    0    25*   100*                           Surface Resistivity**                                                         (ohms per square)                                                             50% R.H.   2.5E12                                                                             1.2E12                                                                             1.2E12                                                                             1.6E12                                                                             1.2E12                                                                             1.1E12                                                                             3.3E13*                                                                             6.5E11                         10% R.H.   5.4E12                                                                             2.7E12                                                                             2.6E12                                                                             3.7E12                                                                             2.5E12                                                                             2.4E12                                                                             2.7E16*                                                                             1.1E13*                        __________________________________________________________________________     *denotes unacceptable value                                                   **2.5E12 means 2.5 × 10.sup.12, etc.                               

EXAMPLE 25

A perfluorosulfonamide polyether compound having the formula of compound2 above is prepared using the following procedure.

A polyether amine (100 grams) (MNPA-750, commercially available fromTexaco), triethylamine (20 grams), and isopropyl ether (100 grams) aredried over potassium hydroxide and then combined in a one-liter flaskfitted with a mechanical stirrer and gas inlet. Perfluorooctanesulfonylfluoride (72 grams; commercially available from 3M as FX-8) is thenadded to the flask and the mixture is heated at reflux under a nitrogenblanket for 3 hours. The mixture is then cooled and neutralized with 50mL. of 50% concentrated hydrochloric acid.

The reaction mixture is then combined with an equal portion ofchloroform, and the chloroform organic layer is washed three times withdeionized water. The organic layer is separated and dried over anhydrousmagnesium sulfate, filtered, and then the chloroform is removed undervacuum. The product (133 grams) is collected as an amber syrup.

Although some sulfonate salt may also be produced in the reaction, thepresence of even major amounts of sulfonate salt is not detrimental tothe ability of the desired perfluorosulfonamide polyether compound tofunction as an antistatic compound in the film constructions of thisinvention. Preparing the perfluorosulfonamide polyether compounds underanhydrous conditions improves the yield of the desired compound. Otheruseful polyoxyalkylene amines which may be used as starting materialsinclude the Jeffamine ED series from Texaco.

EXAMPLES 26-28

The beneficial effect of two lithium perfluorosulfonate salts isdemonstrated in these examples. Eastman 1550 PE (linear low densitypolyethylene) is blended with 0.2% by weight of compound (11) shownabove and 0.1% by weight of Igepal 530 surfactant and then processed ina Brabender extruder. One sample (a control) did not include any lithiumsalt, one sample included 0.1% by weight of CF₃ SO₃ Li, and anothersample included 0.1% by weight of C₄ F₉ SO₃ Li. The temperature profileof the extruder was 200, 240, 250, 255, and 270° C. at 70 RPM screwspeed. Resistivity results after one week are listed in the followingtable.

    ______________________________________                                                        Resistivity (ohm/square)                                      Example   Lithium Salt                                                                              10% R.H.   50% R.H.                                     ______________________________________                                        26        None        6.6 × 10.sup.12                                                                    5.3 × 10.sup.12                        27        CF.sub.3 SO.sub.3 Li                                                                      1.9 × 10.sup.11                                                                    4.8 × 10.sup.10                        28        C.sub.4 F.sub.9 SO.sub.3 Li                                                               4.5 × 10.sup.11                                                                    8.6 × 10.sup.10                        ______________________________________                                    

EXAMPLES 29-31

The beneficial effect of another lithium salt is demonstrated in theseexamples. The same polyethylene resin used in Examples 26-28 was mixedwith 0.4% by weight of compound (14) shown above and 0.1% Tergitol NP-7surfactant and then processed in an extruder. One sample (a control) didnot include any lithium salt, and the other two samples includeddifferent amounts of C₈ F₁₇ SO₃ Li. The extruded polyethylene was bondedto a polyester film having a thin metal conductive layer on its oppositesurface. After three weeks aging the resulting film construction wastested for resistivity of the antistatic (polyethylene layer) and thefilm was heat bonded to itself to form a sealed .envelope. The resultsof the testing are shown in the following table.

    ______________________________________                                                           Resistivity                                                       Lithium Salt                                                                              (ohm/sq.) T-Peel %                                         Example                                                                              Amount      10% R.H.  (lbs.) Delamination                              ______________________________________                                        29     None        2 × 10.sup.11                                                                     3.5    20                                        30     0.02%       4.5 × 10.sup.11                                                                   1.4    1                                         31     0.1%        1.9 × 10.sup.11                                                                   8.2    0                                         ______________________________________                                    

EXAMPLES 32-35

The beneficial effect of C₈ F₁₇ SO₃ Li is also demonstrated in theseexamples. The polyethylene resin of Example 26-28 is blended with 0.4%by weight of compound (11) shown above and different amounts of thelithium salt and then processed in an extruder having a temperatureprofile of 204° C. and 304° C. After the polyethylene was extruded itwas passed over a drum at 132° C. and exposed to ultraviolet light.After aging the film was tested, with the results shown in the followingtable.

    ______________________________________                                                        Resistivity (ohm/square)                                      Example  Lithium Salt 10% R.H.   50% R.H.                                     ______________________________________                                        32       0.01%        5 × 10.sup.11                                                                      4 × 10.sup.11                          33        0.015%      4 × 10.sup.11                                                                      3 × 10.sup.11                          34       0.02%        3 × 10.sup.11                                                                      2 × 10.sup.11                          35       None         3 × 10.sup.12                                                                      1 × 10.sup.12                          ______________________________________                                    

EXAMPLE 36

Several film samples were prepared by dissolving polyethylene (5%) inhot toluene along with varying amounts of different antistatic agentsand lithium salts and then coating the solution onto polyester film at awet coating thickness of 3 mils, after which it is dried at 75° C. forthree minutes and then cooled. The results are shown in the followingtable.

    ______________________________________                                                             A-                                                                            mount                                                    Antistatic                                                                              Li         (wt.    Resistivity (ohm/sq.)                            Agent     Compound   %)      10% R.H.                                                                              50% R.H.                                 ______________________________________                                        None      C.sub.8 F.sub.17 SO.sub.3 Li                                                             0.2     >10.sup.15                                                                            1 × 10.sup.11                      None      C.sub.8 F.sub.17 SO.sub.3 Li                                                             1.0     1 × 10.sup.11                                                                   5 × 10.sup.9                       0.5% Surfona-                                                                           None       --      >10.sup.15                                                                            >10.sup.15                               mine 510*                                                                     0.2% Surfona-                                                                           C.sub.8 F.sub.17 SO.sub.3 Li                                                             0.2     7 × 10.sup.12                                                                   4 × 10.sup.11                      mine                                                                          0.3% Compd 11                                                                           None       --      4 × 10.sup.12                                                                   3 × 10.sup.12                      0.3% Compd 11                                                                           CF.sub.3 SO.sub.3 Li                                                                     0.1     7 × 10.sup.12                                                                   8 × 10.sup.9                       0.3% Compd 11                                                                           C.sub.4 F.sub.9 SO.sub.3 Li                                                              0.1     7 × 10.sup.11                                                                   4 × 10.sup.10                      0.3% Compd 11                                                                           C.sub.8 F.sub.17 SO.sub.3 Li                                                             0.1     6 × 10.sup.11                                                                   8 × 10.sup.10                      ______________________________________                                         *The surfonamine material is an aromatic polyether amine available from       Texaco containing both isopropyloxy groups and oxyethylene groups.       

What is claimed is:
 1. A flexible sheet material being adapted forpackaging an electronic component and being sufficiently transparent toenable visual identification of said component through said sheetmaterial, said sheet material comprising:(a) self-supportingelectrically insulating film; said film having upper and lower majorsurfaces; (b) an electrically conductive layer carried by said uppersurface of said film; (c) an antistatic layer carried by said lowersurface of said film, said antistatic layer comprising a polymer havingdispersed therein a fluoroaliphaticsulfonamide polyether compound whichimparts to said antistatic layer a surface resistivity in the range of10⁷ to 10¹⁴ ohms per square; wherein said polyether compound is of theformula ##STR17## where y and n are each in the range of 0 to 100;wherein y+n is at least 2; wherein R is hydrogen, alkyl, aryl, aralkyl,aminoalkyl, or hydroxyalkyl; wherein R'' and R'''are selected fromethylene and propylene; and wherein R' is alkyl, aryl, aralkyl, alkaryl,aminoalkyl, hydroxyalkyl, or perfluorosulfonamido; and (d) a tie layersecured to said lower surface of said film; wherein said antistaticlayer is secured to said tie layer.
 2. A flexible sheet material inaccordance with claim 1, wherein said tie layer comprises an acrylatepolymer having a volume resistivity of at least 10¹⁰ ohm-centimeters. 3.A flexible sheet material in accordance with claim 1, wherein saidpolymer in said antistatic layer comprises a thermoplastic heat sealablepolymer.
 4. A flexible sheet material in accordance with claim 3,wherein said polyether compound is present in said antistatic layer inan amount of 0.05% to 10% by weight.
 5. A flexible sheet material inaccordance with claim 1, wherein said antistatic layer further comprisesa non-ionic polyether surfactant.
 6. An envelope adapted to receive andprotect an electronic component, said envelope having walls formed of aflexible material having first and second major surfaces, said firstsurface defining an outer surface of the envelope and said secondsurface defining an inner surface of the envelope, wherein said materialcomprises:(a) a self-supporting electrically insulating film having avolume resistivity of at least about 10¹⁰ ohm-centimeters; said filmhaving upper and lower major surfaces; (b) an electrically conductivelayer carried by said upper surface of said film; said conductive layerproviding a surface resistivity no greater than 10⁴ ohms per square; (c)an antistatic layer carried by said lower surface of said film, saidantistatic layer comprising a polymer having dispersed therein afluoroaliphaticsulfonamide polyether compound, wherein said antistaticlayer provides a surface resistivity in the range of 10⁷ to 10¹⁴ ohmsper square; wherein said polyether compound is of the formula ##STR18##where y and n are each in the range of 0 to 100; wherein y+n is at least2; wherein R is hydrogen, alkyl, aryl, aralkyl, aminoalkayl, orhydroxyalkyl; wherein R'' and R''' are selected from ethylene andpropylene; and wherein R' is alkyl, aryl, aralkyl, alkaryl, aminoalkyl,hydroxyalkyl, or perfluorosulfonamido; and (d) a tie layer secured tosaid lower surface of said film; wherein said antistatic layer issecured to said tie layer.
 7. An envelope in accordance with claim 6,wherein said polymer in said antistatic layer comprises a thermoplasticheat sealable polymer.
 8. An envelope in accordance with claim 6,wherein said tie layer comprises an acrylate polymer having a volumeresistivity of at least 10¹⁰ ohm-centimeters.
 9. An envelope inaccordance with claim 8, wherein said acrylate polymer is selected fromthe group consisting of ethylene/acrylic acid copolymers andethylene/methacrylic acid copolymers.
 10. An envelope in accordance withclaim 6, wherein said polyether compound is present in said antistaticlayer in an amount of 0.05% to 10% by weight.
 11. An envelope inaccordance with claim 6, wherein said antistatic layer further comprisesa non-ionic polyether surfactant.
 12. An envelope in accordance withclaim 6, further comprising an abrasion-resistant layer over saidelectrically conductive layer.
 13. A flexible sheet material inaccordance with claim 1, further comprising an abrasion-resistant layerover said electrically conductive layer.
 14. A flexible sheet materialin accordance with claim 1, wherein said electrically insulating filmcomprises polyester and has a thickness in the range of about 10 to 50microns.
 15. A flexible sheet material in accordance with claim 3,wherein said antistatic layer comprises low density polyethylene and##STR19## where y and n are each in the range of 2 to
 20. 16. Anenvelope in accordance with claim 6, wherein said antistatic layercomprises low density polyethylene and ##STR20## wherein y and n areeach in the range of 2 to
 20. 17. A flexible sheet material beingadapted for packaging an electronic component and being sufficientlytransparent to enable visual identification of said component throughsaid sheet material, said sheet material comprising:(a) self-supportingelectrically insulating film; said film having upper and lower majorsurfaces; (b) an electrically conductive layer carried by said uppersurface of said film; (c) an antistatic layer carried by said lowersurface of said film, said antistatic layer comprising a polymer havingdispersed therein a fluoroaliphaticsulfonamide polyether compound whichimparts to said antistatic layer a surface resistivity in the range of10⁷ to 10¹⁴ ohms per square; wherein said polyether compound is of theformula ##STR21## where y and n are each in the range of 0 to 100;wherein y+n is at least 2; wherein R is hydrogen, alkyl, aryl, aralkyl,aminoalkyl, or hydroxyalkyl; wherein R₁ is alkyl; wherein R'' and R'''are selected from ethylene and propylene; and wherein R' is alkoxy; and(d) a tie layer secured to said lower surface of said film; wherein saidantistatic layer is secured to said tie layer.
 18. An envelope adaptedto receive and protect an electronic component, said envelope havingwalls formed of a flexible material having first and second majorsurfaces, said first surface defining an outer surface of the envelopeand said second surface defining an inner surface of the envelope,wherein said material comprises:(a) a self-supporting electricallyinsulating film having a volume resistivity of at least about 10¹⁰ohm-centimeters; said film having upper and lower major surfaces; (b) anelectrically conductive layer carried by said upper surface of saidfilm; said conductive layer providing a surface resistivity no greaterthan 10⁴ ohms per square; (c) an antistatic layer carried by said lowersurface of said film, said antistatic layer comprising a polymer havingdispersed therein a fluoroaliphaticsulfonamide polyether compound,wherein said antistatic layer provides a surface resistivity in therange of 10⁷ to 10¹⁴ ohms per square; ##STR22## where y and n are eachin the range of 0 to 100; wherein y+n is at least 2; wherein R ishydrogen, alkyl, aryl, aralkyl, aminoalkyl, or hydroxyalkyl; wherein R₁is alkyl; wherein R'' and R''' are selected from ethylene and propylene;and wherein R' is alkoxy; and (d) a tie layer secured to said lowersurface of said film; wherein said antistatic layer is secured to saidtie layer.